如何注册与pongo模板一起使用的功能？

Question

I want to be able to register a function in pongo2 to be able to use in the template. I don't want to use it as a filter. I want to call it as a function. How can I go about this? I don't see any method to RegisterFunction like I can RegisterFilter

I have tried to use RegisterFilter but it doesn't fit my exact use-case which is to call a function to get some data and not to filter an input